The invention is concerned with a novel and advantageous device for the flash evaporation of metal within a vacuum chamber whereby the metal is then deposited on a moving or stationary strip, on desired components, and the like.
A number of wire fed flash evaporation devices are known in the prior art. Each of these devices utilizes a pair of electrodes and a resistively heated boat which forms an electrical path between the two electrodes. A description of several such sources can be found in "Vacuum Technology" Research/Development, Feb. 1974, pp. 51 et seq.
While cooling of the electrodes or the bus bars to which the electrodes are often attached is well-known in the art to prevent localized melting and evaporation it has been usual in order to prevent shorting through coolant pipes to use separate coolant streams for each of the electrodes. This, of course, generally requires the introduction and exiting of at least two coolant streams into the vacuum chamber, one for each electrode, thus increasing the chances of leaks. Further, this does not generally provide cooling of the wire feed nozzle and the support which holds it and this can be important in preventing premature melting of the wire adjacent or even within the nozzle. Still further, because of their design it is usually required that a good deal of skill be exercised in taking apart and reassembling the prior art flash evaporation sources for cleaning purposes.
The present invention provides a flash evaporation source which solves many of the problems of prior art sources, requires only a single coolant stream to be introduced into the vacuum chamber, and is easily disassembled for cleaning and easily reassembled. Further, the nozzle through which wire is fed and the support which holds this nozzle are themselves water-cooled so as to provide a more even evaporation of wire which is fed onto a resistively heated boat.